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  1. #11


    Ok guys, I think I am getting close to a resolution for this bs. I changed the fuel filter, and oil filter descent, I have not tried a compression test and I do still partially think injectors but I have to make sure before diving out there to just hand someone $500. I am still experiencing the same problem however after a fuel pressure test I am left baffled. I read a couple of places online that say the pressure should be between 60-66 for my truck, but when we checked mine it only said 50 when I had the truck turned on and I was told that 50 was fine? I thought a couple of things seemed odd when I performed this test and figured I could bring it to y'all's attention to see if anything jumps out at you. I started the test by hooking the guage up to the shader valve under the hood, turned the key to on position and got out to check my pressure..... 0 it said. So I turned the truck on and it slowly works it's way up to 50then I turn the truck off and it sticks to fifty, which led me to believe the FPR and injectors were fine. It threw a weird code yesterday that I got erased that mentioned multiple misfire, then today I got one on p0440 or evaporate vent valve cylinoid. Today I also check the fuel pump relay which was alsos fine. Someone mentioned to me today that when I replaced my distributor cap and rotor that it may have messed the timing up? I have replaced the distributor twice.

  2. #12


    50 is LOW for a Vortec motor should be the 60-66 you mentioned. If the truck has the factory fuel pump it might be the issue. If it stays at pressure for a while after turned off then you're right about the injectors likely not leaking.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

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  3. #13


    i have a 92 chevy silverodo 5.7L 4x4 halfton automatic. in runs real rough when i stop at red lights,& sometimes it stall. in neutral its fine. ive replaced everything i could think of to no evail. compression is good,vacumm good,replaced computer,oil sending unit,brake booster,idel control & many more. dont know what to do next. o & no codes

  4. #14



    You have just described a text book fuel pump pressure test failure! pump should reach full pressure on first key on prime cycle. i am surprised it starts with only 50 PSI. the injector poppets usually won't open much under 60 PSI. i believe spec is 62-66PSI at start and around 55PSI running. BE AWARE! a problem in the pumps power or ground circuit can prevent a good pump from working correctly. ALWAYS TEST THE CIRCUIT BEFORE REPLACING A PART.

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  6. #15


    Haha YES! I had a weird feeling it was the fuel pump but my friend insisted 50 was correct and the prime turn was ok at 0. I appreciate the help I will check the circuit first. Also will a failing fuel pump effect my evap vent valve?

  7. #16


    Off the top of my head. no. why are you asking? did i miss something?

    OH, for carl gee, you should start your own thread. that way more members will see it and possibly be able to help. i'll be watching for it!

  8. #17


    Grahamwk, the fuel pump should run for 2 seconds right after you turn the key to on to prime the fuel rail etc. Pressure on mine reads about 62LBS. If you read 0 that is a problem. You say that when you start the truck your pressure builds up to 50. A bit low. I think its probably fuel pump time.

  9. #18


    That sounds good to me, I've just been stumped for months due to this mis and I'm glad we finally got it figured out I hope lol. Also yes my truck threw an 0440 on the evap vent cylinoid so I wondered if the fuel pump was the reason behind it.

    - - - Updated - - -

    When replacing the fuel pump what all needs to be replaced? Do I just order a pump alone Or do I order the fuel pump assembly. .
    i have also heard about sensors in there that need to be checked.

  10. #19


    P04440 is an EVAP code commonly associated with a large leak. not specific to the vent solenoid that i know of. I'm in a rush right now, so google obd2 p0440 and you will get a good general description. i'll try to elaborate later.

    I prefer the complete hanger assembly with fuel level sender, and always AC DELCO! make sure you use the new gaskets and clean the area good. a leaking gasket at the F/P locking ring can set P0440 or other EVAP codes. fuel tank pressure sensor is in the tank and can cause P0440. bad or loose gas cap can also set same code.

  11. #20


    Oh ok so there is a possibility that something with the fuel pump is rowing the code, good haha. Do the sensors come with the whole assembly?

    - - - Updated - - -

    Lol does it have to be ac delco? Any other good brands for a chevrolet?

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